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West Pacific/2015/11W/Archive/6
Public advisory TROPICAL STORM NANGKA PUBLIC ADVISORY NUMBER 6 WIKI-HURRICANES FORECASTING CENTER 6:00 AM JST SUN JUL 05 2015 ...NANGKA MAINTAINING INTENSITY ON ITS WESTWARD TRACK... SUMMARY OF 6:00 AM JST...21:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...11.2N 165.1E CENTER POSITION CONFIDENCE: HIGH ABOUT 555 MI...895 KM NNE OF PALIKIR, MICRONESIA MAXIMUM SUSTAINED WINDS...40 KT...45 MPH...75 KM/H MINIMUM BAROMETRIC PRESSURE...999 MB...29.50 INCHES PRESENT MOVEMENT...W AT 15 KT...17 MPH...27 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 6:00 am JST, the center of Tropical Storm Nangka was situated near 11.2N, 165.1E, or about 555 miles (895 km) north-northeast of Palikir, Micronesia. Maximum sustained winds were 40 knots (45 mph, 65 km/h), with higher gusts. The minimum barometric pressure was 999 millibars (hPa; 29.50 inHg), and the cyclone was tracking west at 15 knots (17 mph, 27 km/h). Environmental conditions are expected to be generally favorable for steady intensification throughout the forecast period, with the potential for rapid intensification growing after 48 hours. NEXT ADVISORY ------------------- Next complete advisory at 12:00 pm JST. $$ Forecaster TAWX14 Discussion TROPICAL STORM NANGKA PUBLIC ADVISORY NUMBER 6 WIKI-HURRICANES FORECASTING CENTER 6:00 AM JST SUN JUL 05 2015 Tropical Storm Nangka has changed little in organization this morning. Although deep convection has become less ragged since this morning, and although the prominent spiral band within the western semicircle of the cyclone has become more distinct, visible satellite images indicate that the low-level circulation is partially exposed on the western side of the central dense overcast. Recent satellite intensity estimates were T3.0/45kt from both SAB and JTWC, while the recent value from UW-CIMSS ADT was T2.6/37kt. A blend of these data support keeping the initial intensity at 40kt, especially given the lack of any ASCAT or microwave passes. Maps from UW-CIMSS indicate that Nangka is undergoing a low 5 to 10 knots of vertical wind shear. However, visible satellite animations that indicate an exposed center of circulation do not support that statement. One potential hypothesis is that the fast forward motion of the system, at 15 knots toward the west, is creating speed shear. Over the coming days, Nangka is forecast to decelerate some, which should allow the system to regain composure. Wind shear should remain conducive for development, with models not as bullish on higher upper-level winds in the 24-48 hour range as they were yesterday. The only limiting factor may be some mid-level dry air to the cyclone's north, but this is not expected to deter strengthening. The updated WHFC shows Nangka becoming a typhoon within 48 hours and further intensifying into the equivalent of a major hurricane by 96 hours. The tropical cyclone is currently tracking swiftly westward under the influence of a 594dm mid-level ridge to the cyclone's north. This motion is expected to continue for the next 24 hours or so, but a gradual turn toward the west-northwest and northwest is expected throughout the remainder of the forecast period as Nangka moves toward a weakness in the anticyclone. Global modelling is in good agreement, and the updated track forecast is similar to the previous one. INIT 04/2100Z 11.2N 165.1E 40 KT 45 MPH 12H 05/0600Z 11.4N 162.9E 45 KT 50 MPH 24H 05/1800Z 11.7N 160.4E 55 KT 65 MPH 36H 06/0600Z 12.4N 158.0E 65 KT 75 MPH 48H 06/1800Z 13.3N 156.1E 75 KT 85 MPH 72H 07/1800Z 15.5N 152.3E 85 KT 100 MPH 96H 08/1800Z 18.2N 148.5E 95 KT 110 MPH...NEAR NORTHERN MARIANA ISLANDS 120H 09/1800Z 21.2N 144.2E 105 KT 125 MPH...NEAR NORTHERN MARIANA ISLANDS $$ Forecaster TAWX14